The operation of power components can be disrupted by the environment in which they operate, e.g., an artificial or natural radiation environment or an electromagnetic environment. Harmful external factors trigger the creation of parasitic currents by interacting with the material that makes up the component. These may cause the temporary or permanent malfunction of the component and the application that uses it.
Natural or artificial radiation environments (neutrons, protons, heavy ions, flash x-rays, and gamma rays) can disrupt the operation of power components. Such disruptions are due to interactions between the material in the component and particles in the radiation environment. One consequence of these disruptions is the creation of parasitic currents in the component. The size of the resulting parasitic currents depends on where the interactions between the component's material and the particles take place. This produces localized areas where charges collect in the component.
Such attacks by heavy ions and protons are typically encountered, in space, by satellites and launch vehicles. At the lower altitudes where airplanes operate, there is an especially high presence of attacks by neutrons. At sea level, such attacks may also be encountered and may affect onboard electronic components in portable device, or in vehicles.
Power components, such as “power MOSFET” transistors and IGBTs, intrinsically have parasitic bipolar structures. During normal operation of the power component, these parasitic bipolar structures are inactive. When a particle from the natural radiation environment interacts with the component's material, a parasitic current is generated and may make the parasitic bipolar structures busy (shown in FIG. 1).
As shown in FIG. 1, in an N-channel power MOSFET transistor 1, the positive charges created during the particle 2/material 4 interaction 3 will migrate toward the well contact 5 as a result of electric fields and diffusion mechanisms. By moving, these positive charges will generate potential increases locally. Initially blocked, the Source (N)/Wells (P) junction 6 can then be polarized directly.
When blocked, if the well/drain junction is already reverse biased, the Source/Wells/Drain parasitic bipolar transistor 7 becomes busy.
In this situation, a second mechanism is then implemented. This mechanism is called an avalanche mechanism, and it produces additional charges at the well/drain junction with a maximum electric field value. If the electric field conditions are sufficient and the current output is not otherwise reduced, the avalanche mechanism and the injection of carriers by the bipolar transistor are maintained and amplified until the increase in temperature locally following the passage of the current causes physical damage to the component. FIG. 2 is an example of such damage.
Such failures are common to power IGBT and MOSFET structures.
For IGBTs in particular, there is also another, more common component failure known as “latchup”. This “latchup” phenomenon involves the conduction of a parasitic thyristor with an NPNP structure, which exists only in IGBTs and not in MOSFETs, as shown in FIG. 3.
Additionally, for other power structures like diodes, there is no parasitic bipolar structure, but the conditions of the electric field are such that they may still cause a destructive avalanche effect during particle interaction or any other interaction resulting in the generation of charges.
The laser is mainly used as a tool for pre-characterizing the sensitivity of the components to radiation. Like particles in the radiation environment, the laser can generate parasitic currents within components at the appropriate wavelength.
The laser thus provides a very interesting advantage for studying the effect of radiation. Because the spatial resolution of the laser can reach relatively small sizes relative to the basic structures contained in the electronic components, it is possible, as in the case of ion microbeams, to map an electronic component and identify its areas where charges are collected. By varying the beam's focal depth, 3D sensitivity mapping can also be carried out, which is easy using machines.
However, this knowledge is not enough to understand the total behavior of the electronic component with respect to radiation.
The prior art therefore provides a method to overcome this problem by determining the sensitivity of electronic components by means of simulation. Once the component's sensitivity mapping has been established, it is modeled, often as a matrix with four or five dimensions, with X Y Z and a sensitivity coefficient or with X Y Z T and a sensitivity coefficient. The component model is then subjected to a simulated attack, and its simulated response is measured. For example, schematically, if at a given time T, a simulated ion (either a primary ion or an ion produced from a nuclear reaction) passes through a basic area with XYZ coordinates, and if, at that time, that same basic area has a sensitivity s, the quality value s is assigned to the component. This experiment is then repeated for another simulated ion. Therefore, over a given period of study, as the time varies and the application initiated by the component runs, the values are collected and, then, perhaps after a given measurement duration, the measured quality values are compiled to determine the actual quality of the component. By doing this, rather than having a map that is subject to speculation, we get a true measure of quality.